Detection of Clostridium difficile antigen and toxin in stool specimens: Comparison of the C. difficile quik chek complete enzyme immunoassay and GeneXpert C. difficile polymerase chain reaction assay
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Background/Aims: Accurate and rapid laboratory diagnosis of Clostridium difficile infections (CDI) remains a significant challenge. A two‑step algorithm for detection of toxigenic C. difficile in stool based on initial screening for glutamate dehydrogenase assay followed by confirmation by toxin A+B detection using an enzyme immunoassay (EIA) or molecular assay has been proposed. We aimed to evaluate the C. difficile Quik Chek Complete® (QCC‑EIA) versus the GeneXpert® C. difficile polymerase chain reaction (PCR) assay in this two‑step algorithm. Materials and Methods: Two hundred and ten liquid stool samples obtained between June 2014 and June 2015 from patients suspected of CDI were tested by the QCC‑EIA and GeneXpert PCR assay. The GeneXpert assay was used as the reference standard to calculate the QCC‑EIA sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV). Results: Of the 210 stool samples tested, 43 (20.5%) were positive by QCC‑EIA, while 31 (14.8%) were positive by GeneXpert assay. The sensitivity and specificity of the QCC‑EIA were found to be 100 and 93%, respectively; the PPV and NPV were 72 and 100%, respectively. The binary toxin was detected in 12 (38.7%) and tcdC gene deletion in 3 (9.6%). Conclusions: The low specificity of QCC‑EIA makes it less reliable as a confirmatory test for CDI diagnosis. This test may be used as a screening test in a two‑step algorithm when combined with a molecular assay or another confirmatory test.